Implement strlcpy and strlcat [BZ #178]

These functions are about to be added to POSIX, under Austin Group
issue 986.

The fortified strlcat implementation does not raise SIGABRT if the
destination buffer does not contain a null terminator, it just
inherits the non-failing regular strlcat behavior.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

50 files changed, 560 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 23051cf139..7a4df85f08 100644
--- a/NEWS
+++ b/NEWS
@@ -35,6 +35,9 @@ Major new features:
   The symbol names follow the AArch64 vector ABI, they are declared
   in math.h and have to be called manually at this point.
 
+* The strlcpy and strlcat functions have been added.  They are derived
+  from OpenBSD, and are expected to be added to a future POSIX version.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * In the Linux kernel for the hppa/parisc architecture some of the
diff --git a/debug/Makefile b/debug/Makefile
index 096df27aeb..55e2aadec9 100644
--- a/debug/Makefile
+++ b/debug/Makefile
@@ -84,6 +84,8 @@ routines = \
   stpncpy_chk \
   strcat_chk \
   strcpy_chk \
+  strlcat_chk \
+  strlcpy_chk \
   strncat_chk \
   strncpy_chk \
   swprintf_chk \
diff --git a/debug/Versions b/debug/Versions
index a6628db356..94dfa5f428 100644
--- a/debug/Versions
+++ b/debug/Versions
@@ -58,6 +58,10 @@ libc {
   GLIBC_2.25 {
     __explicit_bzero_chk;
   }
+  GLIBC_2.38 {
+    __strlcat_chk;
+    __strlcpy_chk;
+  }
   GLIBC_PRIVATE {
     __fortify_fail;
   }
diff --git a/debug/strlcat_chk.c b/debug/strlcat_chk.c
new file mode 100644
index 0000000000..888a62fad5
--- /dev/null
+++ b/debug/strlcat_chk.c
@@ -0,0 +1,31 @@
+/* Fortified version of strlcat.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+
+/* Check that the user-supplied size does not exceed the
+   compiler-determined size, and then forward to strlcat.  */
+size_t
+__strlcat_chk (char *__restrict s1, const char *__restrict s2,
+	       size_t n, size_t s1len)
+{
+  if (__glibc_unlikely (s1len < n))
+    __chk_fail ();
+
+  return __strlcat (s1, s2, n);
+}
diff --git a/debug/strlcpy_chk.c b/debug/strlcpy_chk.c
new file mode 100644
index 0000000000..768a3af686
--- /dev/null
+++ b/debug/strlcpy_chk.c
@@ -0,0 +1,31 @@
+/* Fortified version of strlcpy.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+
+/* Check that the user-supplied size does not exceed the
+   compiler-determined size, and then forward to strlcpy.  */
+size_t
+__strlcpy_chk (char *__restrict s1, const char *__restrict s2,
+	       size_t n, size_t s1len)
+{
+  if (__glibc_unlikely (s1len < n))
+    __chk_fail ();
+
+  return __strlcpy (s1, s2, n);
+}
diff --git a/debug/tst-fortify.c b/debug/tst-fortify.c
index 9f962f2a75..0f823a85d0 100644
--- a/debug/tst-fortify.c
+++ b/debug/tst-fortify.c
@@ -535,6 +535,20 @@ do_test (void)
   strncpy (a.buf1 + (O + 6), "X", l0 + 4);
   CHK_FAIL_END
 
+  CHK_FAIL_START
+  strlcpy (a.buf1 + (O + 6), "X", 4);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
+  strlcpy (a.buf1 + (O + 6), "X", l0 + 4);
+  CHK_FAIL_END
+
+  {
+    char *volatile buf2 = buf;
+    if (strlcpy (buf2, "a", sizeof (buf) + 1) != 1)
+      FAIL ();
+  }
+
 # if !defined __cplusplus || defined __va_arg_pack
   CHK_FAIL_START
   sprintf (a.buf1 + (O + 7), "%d", num1);
@@ -558,6 +572,23 @@ do_test (void)
   CHK_FAIL_START
   strncat (a.buf1, "ZYXWV", l0 + 3);
   CHK_FAIL_END
+
+  memset (a.buf1, 0, sizeof (a.buf1));
+  CHK_FAIL_START
+  strlcat (a.buf1 + (O + 6), "X", 4);
+  CHK_FAIL_END
+
+  memset (a.buf1, 0, sizeof (a.buf1));
+  CHK_FAIL_START
+  strlcat (a.buf1 + (O + 6), "X", l0 + 4);
+  CHK_FAIL_END
+
+  {
+    buf[0] = '\0';
+    char *volatile buf2 = buf;
+    if (strlcat (buf2, "a", sizeof (buf) + 1) != 1)
+      FAIL ();
+  }
 #endif
 
 
diff --git a/include/string.h b/include/string.h
index 673cfd7272..0c78ad2539 100644
--- a/include/string.h
+++ b/include/string.h
@@ -88,6 +88,10 @@ libc_hidden_proto (__stpcpy)
 # define __stpcpy(dest, src) __builtin_stpcpy (dest, src)
 #endif
 libc_hidden_proto (__stpncpy)
+extern __typeof (strlcpy) __strlcpy;
+libc_hidden_proto (__strlcpy)
+extern __typeof (strlcat) __strlcat;
+libc_hidden_proto (__strlcat)
 libc_hidden_proto (__rawmemchr)
 libc_hidden_proto (__strcasecmp)
 libc_hidden_proto (__strcasecmp_l)
diff --git a/string/Makefile b/string/Makefile
index 2eef6f1dfc..0ad276cc6a 100644
--- a/string/Makefile
+++ b/string/Makefile
@@ -92,6 +92,8 @@ routines := \
   strerrorname_np \
   strfry \
   string-inlines \
+  strlcat \
+  strlcpy \
   strlen \
   strncase \
   strncase_l \
@@ -177,6 +179,8 @@ tests := \
   tst-inlcall \
   tst-memmove-overflow \
   tst-strfry \
+  tst-strlcat \
+  tst-strlcpy \
   tst-strlen \
   tst-strtok \
   tst-strtok_r \
diff --git a/string/Versions b/string/Versions
index 864c4cf7a4..c56e372a3c 100644
--- a/string/Versions
+++ b/string/Versions
@@ -92,4 +92,8 @@ libc {
   GLIBC_2.35 {
     __memcmpeq;
   }
+  GLIBC_2.38 {
+    strlcat;
+    strlcpy;
+  }
 }
diff --git a/string/bits/string_fortified.h b/string/bits/string_fortified.h
index 9900df6104..23ef064168 100644
--- a/string/bits/string_fortified.h
+++ b/string/bits/string_fortified.h
@@ -139,4 +139,40 @@ __NTH (strncat (char *__restrict __dest, const char *__restrict __src,
 				  __glibc_objsize (__dest));
 }
 
+#ifdef __USE_MISC
+extern size_t __strlcpy_chk (char *__dest, const char *__src, size_t __n,
+			     size_t __destlen) __THROW;
+extern size_t __REDIRECT_NTH (__strlcpy_alias,
+			      (char *__dest, const char *__src, size_t __n),
+			      strlcpy);
+
+__fortify_function size_t
+__NTH (strlcpy (char *__restrict __dest, const char *__restrict __src,
+		size_t __n))
+{
+  if (__glibc_objsize (__dest) != (size_t) -1
+      && (!__builtin_constant_p (__n > __glibc_objsize (__dest))
+	  || __n > __glibc_objsize (__dest)))
+    return __strlcpy_chk (__dest, __src, __n, __glibc_objsize (__dest));
+  return __strlcpy_alias (__dest, __src, __n);
+}
+
+extern size_t __strlcat_chk (char *__dest, const char *__src, size_t __n,
+			     size_t __destlen) __THROW;
+extern size_t __REDIRECT_NTH (__strlcat_alias,
+			      (char *__dest, const char *__src, size_t __n),
+			      strlcat);
+
+__fortify_function size_t
+__NTH (strlcat (char *__restrict __dest, const char *__restrict __src,
+		size_t __n))
+{
+  if (__glibc_objsize (__dest) != (size_t) -1
+      && (!__builtin_constant_p (__n > __glibc_objsize (__dest))
+	  || __n > __glibc_objsize (__dest)))
+    return __strlcat_chk (__dest, __src, __n, __glibc_objsize (__dest));
+  return __strlcat_alias (__dest, __src, __n);
+}
+#endif /* __USE_MISC */
+
 #endif /* bits/string_fortified.h */
diff --git a/string/string.h b/string/string.h
index 4927879ecf..c0773d11d8 100644
--- a/string/string.h
+++ b/string/string.h
@@ -501,6 +501,19 @@ extern char *stpncpy (char *__restrict __dest,
      __THROW __nonnull ((1, 2));
 #endif
 
+#ifdef __USE_MISC
+/* Copy at most N - 1 characters from SRC to DEST.  */
+extern size_t strlcpy (char *__restrict __dest,
+		       const char *__restrict __src, size_t __n)
+  __THROW __nonnull ((1, 2)) __attr_access ((__write_only__, 1, 3));
+
+/* Append SRC to DEST, possibly with truncation to keep the total size
+   below N.  */
+extern size_t strlcat (char *__restrict __dest,
+		       const char *__restrict __src, size_t __n)
+  __THROW __nonnull ((1, 2))  __attr_access ((__read_write__, 1, 3));
+#endif
+
 #ifdef	__USE_GNU
 /* Compare S1 and S2 as strings holding name & indices/version numbers.  */
 extern int strverscmp (const char *__s1, const char *__s2)
diff --git a/string/strlcat.c b/string/strlcat.c
new file mode 100644
index 0000000000..dce4c255d1
--- /dev/null
+++ b/string/strlcat.c
@@ -0,0 +1,59 @@
+/* Append a null-terminated string to another string, with length checking.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/l